Light emitting diodes (LEDs) and other solid state light sources require a constant direct current (DC) voltage or current to operate optimally. During operation, the light source must be protected from line-voltage fluctuations. Changes in the forward voltage of a solid state light source can produce a disproportional change in current, which in turn can cause light output to vary, as light output is proportional to current and is rated for a current range. If current exceeds the manufacturer recommendations, the solid state light source may become brighter, but the light output may degrade at a faster rate due to higher temperatures within the device. This leads to a shorter useful life. Solid state devices in certain environments require a programmable driver with sufficient regulation to permit a wide range of operation and also provide dimming capabilities.
Programmable drivers enable dimming of the light sources. The solid state light sources are easily integrated with circuits to control dimming so that these functions respond to preset commands or occupant presence or commands. Dimming drivers dim the light sources by reducing the forward current, pulse width modulation (PWM) via digital control, or more sophisticated methods. Most dimming drivers operate using the PWM method. With this method, the frequency could range from a hundred modulations per second to as high as hundreds of thousands of modulations per second, so that the light source appears to be continuously lighted without flicker.